I thought I had done this once before but I'm beginning to think I was smoking some serious crack that day.

In the Identifiers field I have a large number of books that show uri:http|(whatever the address is) and I have a large number that show url:http|(whatever the address is) I want to change all of the http addresses listed as uri's to be listed as url's. I thought I had done this with Search & Replace but for the life of me I can't figure out how. Is this possible or am I doomed to fixing all 740 of them by hand?

I didn't know you could do this, but I just played and found out how. On the search and replace tab, do the following"

- Select "identifiers" as the "Search field"
- Select "Regular Expression" for the Search mode
- Select "uri" in the first "Identifier type"
- Select "identifiers" as the "Search field" and the "Destination field"
- Enter "url" in the second identifier type

I didn't know you could do this, but I just played and found out how. On the search and replace tab, do the following"

- Select "identifiers" as the "Search field"
- Select "Regular Expression" for the Search mode
- Select "uri" in the first "Identifier type"
- Select "identifiers" as the "Search field" and the "Destination field"
- Enter "url" in the second identifier type

I left everything else alone and press OK and the changes were made.

I tried that and it didn't show up in the text box so I didn't press ok

Technically, yes, the links are fine but FanFictionDownloader doesn't recognize the uri identifier links as valid urls. Although JimmXinu did just provide me with a new version that will recognize both uri and url identifiers as valid urls.

I didn't know you could do this, but I just played and found out how. On the search and replace tab, do the following"

- Select "identifiers" as the "Search field"
- Select "Regular Expression" for the Search mode
- Select "uri" in the first "Identifier type"
- Select "identifiers" as the "Search field" and the "Destination field"
- Enter "url" in the second identifier type

I left everything else alone and press OK and the changes were made.

Actually what that does is add a second identifier under url in that field. ie:

You start out with the following in the identifier field:
uri:http|//www.archiveofourown.org/works/154933/

Run through the steps you outlined above and you end up with:
uri:http|//www.archiveofourown.org/works/154933/, url:http|//www.archiveofourown.org/works/154933/

Technically this does get the job done for me as it now has the url identifier and the FFDL plugin will recognize it. Unfortunately I'm OCD enough that having both in there bugs the hell out of me. Thankfully I found excellent directions from Chaley here: A Way To Mass Delete IDs on how to get rid of the identifiers I don't want.